Method for making perforating strips



' May 12, 1964 H. s. BOYD 3,132,540

METHOD FOR MAKING PERFORATING STRIPS Filed Nov. 29, 1961 IN V EN TOR.

Harry 5. 50 /0 R056/"7L J. Pei/ch ATTY.

United States Patent 3,132 540 METHOD F OR MAKING TERFGRATING STRIPSHarry S. Boyd, 6525 E. 24th St., Tulsa, Okla. Filed Nov. 29, 1961, Ser.No. 155,638 4 Claims. (Cl. 76-l01) The present invention relates tomethods for making perforating strips, more particularly of the typedisclosed in my copending patent application, Serial No. 155,657, filedNovember 29, 1961, entitled Apparatus for Perforating Sheets.

The object of the present invention is the provision of methods formaking perforating strips, which will be relatively simple andinexpensive to practice and which will produce perforating strips ofuniformly even dimensions and desirably sharp edges.

Other objects and advantages of the present invention will becomeapparent from a consideration of the following description, taken inconnection with the accompanying drawing, in which:

FIGURE 1 is a fragmentary perspective view of a length of preformedblank from which the perforating strip is made;

- FIGURES 2-5 are fragmentary cross-sectional views of the structure ofFIGURE 1, showing alternative Ways of forming the final product;

FIGURES 6-9 are plan views of the structure of FIG URES 2-5,respectively; and

FIGURES -13 are fragmentary perspective views of the finished productcorresponding to FIGURES 2-5 and 6-9, respectively.

Referring now to the drawing in greater detail, there is shown aperforating strip blank 1 which has been formed by rolling from a lengthof metal wire. Blank 1 comprises a thin flat strip 3 having oppositeparallel rounded side edges 5 and 7 and a flat upper surface 9 parallelto a fiat under surface 11. A multiplicity of projections 13 is disposedin a straight line along upper surface 9. Each projection 13 hasgenerally pyramidal form bounded on its exposed sides by flat surfaces15, 17, 19 and 21. Projections 13 thus have coplanar edges 23 extendingparallel to the length of but perpendicular to the plane of strip 3, theedges 23 being defined on one side of each projection 13 by the junctionof surfaces 15 and 19, and on the other side of each projection 13 bythe junction of surfaces 17 and 21. Projections 13 also have sharp edgesextending generally transverse to edges 23 and disposed in parallelplanes perpendicular both to the length and to the plane of strip 3.Thus, edge 25 is defined on one side of each projection 13 by thejunction of surfaces 15 and 17, and on the other side of each projection13 by the junction of surfaces 19 and 21. Edges 23 lie on the rnidplane27 of the group of projections 13.

As indicated above, blank 1 is formed by rolling between two cylindricalrollers, one of which forms the plain under surface 11 and thus has aplain cylindrical periphery, and the other of which forms upper surface9 with projections 13 and for this purpose has a cylindrical peripherywhich is provided with a multiplicity of indentations complementary toprojections 13. When wire is run between these two opposed rollers (notshown), the wire is flattened and at the same time projections 13 areformed. It should be noticed that that portion of the wire which is notconsumed in forming projections 13 is formed into fiat strip 3 with theoriginal round edges of the wire converted into rounded side edges 5 and7 of the strip. It should also be noted that projections 13' are spacedfrom both side edges 5 and 7 but are closer to side edge 5 than to sideedge 7, and that projections 13 are bisymrnetric on both sides of themidplane 27. By this arrangement, it is possible to roll for examplecircular wire into the shape shown in FIGURE 1 without distorting thewire and without causing it to twist or turn upon the formation ofprojections 13 thereon. The projections are thus formed with roundedcontours immediately adjacent their original apices 29 and the rollingoperation is facilitated by making no attempt to roll these apices tosharp points in the blank as originally formed.

The second step is to grind blank 1 into final form, and this is done ina single grinding operation which reduces blank 1 from the form shown inFIGURE 1, or shown in dotted line in FIGURES 2-9, to the form shown infull line in FIGURES 2-9 or in FIGURES 10-13. Specifically, side edge 5and at least half of each projection 13 are ground away on a bias, untilwhat remains is a ground uniplanar surface 31 that is disposed at anacute angle to surfaces 9 and 11 and to the plane of strip 3 and thatextends from surface 11 to a new apex 33 on each projection 13, the newapex 33 being disposed intermediate the length of what formerly was edge25 on the same side of strip 3 as side edge 7 thereof.

FIGURES 2-5 show respectively in side cross section and FIGURES 6-9 showrespectively in plan four of the many ways in which this grinding stepmay be performed. In general, of course, to produce the most slender andthe tallest teeth, the angle between newly ground surface 31 andmidplane 27 should be the least, as in FIGURES 2 and 3. FIGURES 2 and 3differ from each other in that in FIGURE 2 ground surface 31 intersectsupper surface 9 at midplane 27, while in FIGURE 3 newly ground surface31 intersects under surface 11 at midplane 27. The resulting teeth areof the same height in either case, which means that their apices 33 arethe same distance from strip 3 as seen in FIGURES 2 and 3. As a result,therefore, surface 31 in FIGURE 3 can be a little steeper and theresulting teeth a little thinner than in the case of FIG- URE 2.

Similarly, in FIGURES 4 and 5, surface 31 is steeper in FIGURE 4 than inFIGURE 5, and in FIGURE 5 surface 31 intersects rnidplane 27 at undersurface 11, while in FIGURE 4 the surface 31 intersects midplane 2.7 atupper surface 9. Apices 33 in FIGURES 4 and 5 are at the same height,but this height is less than in the case of FIGURES 2 and 3.

Representative inclinations of surfaces 31 in FIGURES 2-5 from thevertical might be, for example, 11, 8, 21, and 18, respectively.

FIGURES 6-9 show in phantom line the material ground away during theformation of surfaces 31, and also illustrate the relative merits ofcausing surfaces 31 to intersect midplane 27 at upper surface 9 or undersurface 11. When surface 31 intersects midplane 27 at upper surface 9,the newly-formed serrated edges along surface 31 meet each other at thebottom of V-shaped grooves in surface 31, as in FIGURES 2 and 4; whereasin FIGURES 3 and 5, when the surfaces 31 intersect midplane 27 at undersurface 11 and the width of the base of the final tooth is less thanhalf the width of the base of the original tooth, the convergingadjacent edges of surface 31 do not meet but rather are spaced apart atsurface 9, thereby to provide gaps between the bases of the final teeth,as seen in FIGURES 7 and 9. These gaps are useful if the material to beperforated is relatively weak, as the gaps provide wider and hencestronger bridges between perforations than in the case of teeth thatmeet at their bases.

As seen in FIGURES 10-13, it is thus possible to provide long slenderteeth or short stubby teeth by manipulation of the angle of surface 31;and it is possible to provide teeth that are either immediately adjacenteach other or spaced apart at their bases depending on how much of thematerial of projections 13 is cut away.

The grinding step is not a laborious one, for the strip material of thepresent invention is really quite small and is greatly enlarged in thedrawings for clarity of illustration.

For example, flat strip 3 might have a thickness of only 0.006 inch. Ifprojection 13 were ground down, say, 0.007 inch at an angle of 11 as inthe embodiment of FIGURE 2, then new apex 33 would have a height abovesurface 11 of 0.023 inch. This same height of new apex 33 could beachieved by grinding down as in FIGURE 3 at an angle of 8 for groundsurface 31. In FIGURE 4, if surface 31 were ground at an angle from thevertical of 21 as shown, then the lower height of new apex 33 would beachieved by grinding through only 0.010 inch of projection 13. The sameheight of apex 33 in FIGURE would be achieved by grinding surface 31 atan angle of 18, In any event, however, it should be noted that all ofsurfaces 15 and 17 and part of surfaces 19 and 21 are ground away, sothat everything on the same side of midplane 27 as the nearer of theedges 5 and '7 will be ground away, and in addition part of what lies onthe other side of midplane 27.

From a consideration of the foregoing disclosure, it will be obviousthat all of the initially recited objects of the present invention havebeen achieved.

Although the present invention has been described and illustrated inconnection with preferred embodiments, it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit of the invention, as those skilled in this art will readilyunderstand. Such modifications and Variations are considered to bewithin the purview and scope of the present invention as defined by theappended claims.

What is claimed is:

1. A method for making perforating strips, comprising rolling a metalfilament into the form of a thin flat strip having a multiplicity ofprojections disposed along the length of the strip and extending awayfrom one side of the strip and spaced from both side edges of the stripand being tapered from greatest size at their bases to least size attheir original apices, and grinding away one side edge of the strip andadjacent portions of the projections to leave a ground uniplanar surfacethat is displaced at an acute angle to the remainder of the flat stripand that extends from the side of the strip opposite the projections tonew apices of the projections which are nearer the strip than theoriginal apices.

2. A method as claimed in claim 1, in which said grinding is continueduntil at least half of the width of the base of the projection measuredtransversely of the strip has been ground away.

3. A method as claimed in claim 1, in which said projections are formedhaving sharp edges disposed in the planes which are perpendicular to thelength of the strip and which include the original apices, the newapices lying on and being disposed intermediate the length of saidedges.

4. A method as claimed in claim 2, the projections as formed prior togrinding being bisymmetrical about the plane which is perpendicular tothe strip and which includes the original apices.

Gaston July 13, 1869 Boyd July 8, 1958

1. A METHOD FOR MAKING PERFORATING STRIPS, COMPRISING ROLLING A METALFILAMENT INTO THE FORM OF A THIN FLAT STRIP HAVING A MULTIPLICITY OFPROJECTIONS DISPOSED ALONG THE LENGTH OF THE STRIP AND EXTENDING AWAYFROM ONE SIDE OF THE STRIP AND SPACED FROM BOTH SIDE EDGES OF THE STRIPAND BEING TAPERED FROM GREATEST SIZE AT THEIR BASES TO LEAST SIZE ATTHEIR ORIGINAL APICES, AND GRINDING AWAY ONE SIDE EDGE OF THE STRIP ANDADJACENT PORTIONS OF THE PROJECTIONS TO LEAVE A GROUND UNIPLANAR SURFACETHAT IS DISPLACED AT AN ACUTE ANGLE TO THE REMAINDER OF THE FLAT STRIPAND THAT EXTENDS FROM THE SIDE OF THE STRIP OPPOSITE THE PROJECTIONS TONEW APICES OF THE PROJECTIONS WHICH ARE NEARER THE STRIP THAN THEORIGINAL APICES.